meaning and origins
There are several proposed origins for the name:
from the Middle English personal name Dere which variously meant dear (beloved) or deer, and which in turn was derived from Old English deora.
a variant of the Irish Dearmond which is an anglicized version of a Gaelic name meaning a descendant of Duibhdhiorma which means black trooper.
an Americanised spelling of the German Diermann or Thiermann, from a shortened version of the German name Dietrich or from tier - meaning game in the animal sense. All of which is really the same as the first explanation.
Dearman, Derman, Deerman, Darman, Dorman
distribution in England and Wales
In 1891 the Dearmans were centred in Hertfordshire and London, followed by Middlesex and Yorkshire with the rest scattered here and there.
Hertfordshire, Enfield, Australia, Bridgend, London
This side of the family has had troubled times in the past. Currently I have only been able to trace the family back to the end of the eighteenth century in Essendon, Hertfordshire. This original family had major troubles, with no less than three of the sons being transported to various parts of Australia for theft (indeed all the sons I know about). Those who remained behind struggled, but eventually became respectable bricklayers, plasterers and builders. Their heartland seems to be in Enfield, Middlesex, but one of their number wandered to Mansfield, Nottinghamshire and Bridgend in Wales, whilst his son returned in the mid twentieth century to the London area and now, his son has travelled back to Australia.
The only bearers of the name in this particular direct line, now all live in Australia. Maybe the tree should have been a gum tree!